Now, the background art will be described.
FIG. 1 is a front view illustrating a typical barrel coil spring.
As illustrated in FIG. 1, the barrel coil spring 1, which is, for example, a miniblock spring, which has a smaller diameter at opposite ends thereof than in the middle thereof, a side load coil spring, which has a gradually reduced diameter from the middle to the opposite ends thereof, or the like, has a smaller diameter at opposite ends thereof than in the middle thereof. Thus, when a spring material is coiled from one end thereof to the other end thereof at one time using a coiler, it cannot be removed from the coiler. For this reason, the spring material is coiled once from one end thereof to the middle thereof using the coiler, and then from the other end thereof to the middle thereof once in a separate subsequent step. Then, the middle part of the coiled spring material is pressed using a bending press. Thereby, the barrel coil spring is manufactured.
The process of manufacturing such a barrel coil spring will be described below in detail with reference to FIG. 2.
FIG. 2 is a diagram explaining the conventional process of manufacturing a barrel coil spring.
As illustrated in FIG. 2, a spring material 2 is coiled from one end thereof to the middle thereof using a coiler 3. Thereby, one side of the spring material 2 is coiled first.
In this manner, after one side of the spring material 2 is coiled first, the spring material 2 is separated from the coiler 3. Next, the coiled spring material 2 is coiled from the other end thereof to the middle thereof using the coiler 3 so as to be coiled in the opposite direction relative to the first side thereof. Thereby, the other side of the spring material 2 is coiled.
As described above, after the opposite sides of the spring material 2 are coiled such that the directions thereof are opposite each other, the coiled spring material is separated from the coiler 3, and the uncoiled middle part of the spring material 2 is pressed using a bending press 4. Thereby, the barrel coil spring 1 is manufactured in a desired shape.
However, when the barrel coil spring 1 is manufactured using this method, the spring material 2 must be coiled twice at the opposite sides thereof. As such, the number of working processes is increased, and it takes a lot of time to manufacture the barrel coil spring 1. As a result, the productivity of the barrel coil spring is remarkably reduced.